Persona – a composite profile of an imaginary person which represents one user group.
Scenarios – stories of personas using the site in their normal context to accomplish their goals.
Personas and Scenarios are covered in BGW 2.
Use Cases – detailed description of a typical task a user will try to accomplish. Includes the steps the user will take and the system’s response to each step.
Task Analysis – breakdown of what it takes to accomplish a task into sub-tasks and specific steps.
Use cases and Task Analysis are covered in BGW 4.